Flags fluttered in a stiff breeze and men in uniform snapped to attention yesterday as three coffins carrying what are believed to be the remains of American soldiers killed in Cambodia during the Vietnam War were loaded onto a C-17 cargo plane destined for Hawaii.

There, forensics experts with the Joint POW/MIA Accounting Command (JPAC) will determine whether the remains contained inside the boxes should be added to the tally of the 37 missing American bodies so far recovered in the Kingdom.

There are still 53 unaccounted-for Americans believed to have died in Cambodia during an off-and-on military presence that stretched from the late 1960s into the mid-’70s.

Speaking at the ceremony at Phnom Penh International Airport, US Ambassador William Todd noted a personal connection to the conflict that claimed the men’s lives, before thanking the members of Cambodian POW/MIA Committee who aided in the effort to recover the remains.

“As the son of a combat helicopter pilot who served in Vietnam twice, I am truly privileged to be a part of this important ceremony,” Todd said.

“The United States formally requested the assistance of the Royal Government of Cambodia in conducting joint recovery operations in 1992,” he added. “Since then, Cambodia has graciously assisted with the recoveries and return of the remains of Americans who otherwise may have remained lost forever.”

US embassy spokesman Sean McIntosh said yesterday that the remains were located in Kampong Cham province, and that while they were contained in three coffins, the number and identities of the casualties will not be confirmed until the JPAC has completed its analysis.

The men, he added, were believed to have died in a helicopter crash.

Sieng Lapresse, chairman of the Cambodian POW/MIA Committee, told reporters yesterday that the site where the remains were found had been identified by a Vietnamese witness, and called the country’s joint efforts to recover missing remains “not a political issue, but absolute cooperation on a humanitarian issue”.

“I am honoured to be at the repatriation ceremony of the remains of these possible Americans missing in Cambodia,” he said. “Today marks another day of achievement for the joint Cambodian- American humanitarian mission accounting for Americans missing in Cambodia.”

Questions about the procedure for locating missing remains were referred to JPAC headquarters, which had not responded as of press time.

However, military police spokesman Kheng Tito said yesterday that he used to accompany JPAC search operations in Cambodia, and said that such searches were usually US-led, with Cambodian partners providing security and support.

“The US conducted an investigation of the site from their own information, and documented it, and went down to interview possible witnesses,” he said. “They spent a lot of time; they spent a lot of money.”

US military involvement in Cambodia began in the late 1960s with an extensive bombing campaign in the east of the country aimed at destroying bases and supply lines being used by North Vietnamese troops. Eventually it expanded its involvement to offering air support to Cambodia’s Lon Nol regime against encroaching Khmer Rouge forces. That air support was ultimately discontinued, and the US withdrew from Vietnam in 1975 with the fall of Saigon – now Ho Chi Minh City.

However, its last military action in the region actually occurred on Cambodia’s Koh Tang, just days after Saigon’s fall, when 41 US servicemen were killed trying to rescue the crew of the container ship Mayaguez – an incident that has become something of a dark spot on JPAC’s record of recovering missing Americans.

A 2011 memo from forensic anthropologist Jay Silverstein to the JPAC maintained there had been “a pattern of malfeasance of duty and abuse of scientific ethics” in previous efforts to recover remains from Koh Tang, including the failure to keep records of the excavations.

JPAC was also unable to comment on whether efforts to recover the bodies from Koh Tang – which was recently leased to a Russian developer – were ongoing.

Security specialist John Muller, himself a former US special forces member and commander of the local Veterans of Foreign Wars post – which is named after the Mayaguez – said that he planned to make an informal trip to the island in the coming months.

“This year, I plan to hire a boat from the navy, which they did several years ago, and to bring some of us out to conduct a search, or at least give some reverence,” he said. “But in terms of going out there with a shovel and a sieve, the US government, that has to all be done through them.”